Transcriptional regulation of MHC class I gene expression in rat oligodendrocytes.
MHC class I molecules are normally expressed at very low levels in the brain and their up-regulation in response to cytokines and viral infections has been associated with a number of neurological disorders. Here we demonstrate that the down-regulation of surface class I molecules in differentiated primary rat oligodendrocytes was accompanied by reduced steady-state levels of class I heavy-chain mRNA. Transient expression assays were performed in oligodendrocytes and fibroblasts, using a mouse H-2Kb class I promoter chloramphenicol acetyltransferase plasmid termed pH2KCAT (which contained 5'-flanking sequences from -2033 to +5 bp of the H-2Kb gene relative to the transcriptional start site at +1 bp). These assays showed that H-2Kb promoter activity was reduced in oligodendrocytes but not in class I-expressing fibroblasts. H-2Kb promoter activity was up-regulated in oligodendrocytes co-transfected with a plasmid expression vector encoding the transcriptional activator tax of human T-cell leukaemia virus type I, showing that down-regulation of promoter activity was reversible. Deletion mutant analysis of the H-2Kb promoter revealed the presence of negative regulatory elements that were functional in oligodendrocytes at -1.61 to -1.07 kb and -242 to -190 bp. Deletion of sequences in pH2KCAT encompassing the downstream element totally abolished promoter activity in both oligodendrocytes and fibroblasts, whereas a deletion within the upstream negative regulatory element increased promoter activity specifically in oligodendrocytes. The upstream negative regulatory element also down-regulated a linked heterologous herpes simplex virus thymidine kinase promoter in oligodendrocytes, but not in fibroblasts. Gel retardation assays using overlapping DNA probes that spanned the entire -1.61 to -1.07 kb region revealed the presence of a number of DNA-binding activities that were present in oligodendrocyte, but not in fibroblast nuclear extracts.
Mavria
G
G
School of Biochemistry and Molecular Biology, University of Leeds, Leeds, LS2 9JT, U.K.
Hall
K T
KT
Jones
R A
RA
Blair
G E
GE
D000818:Animals; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000378:metabolism; D005786:Gene Expression Regulation; D005805:Genes, MHC Class I; D006183:H-2 Antigens / Q000235:genetics*; D051379:Mice; D009687:Nuclear Proteins / Q000378:metabolism; D009836:Oligodendroglia / Q000502:physiology*; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D017384:Sequence Deletion; D014158:Transcription, Genetic
D004268:DNA-Binding Proteins; D006183:H-2 Antigens; D009687:Nuclear Proteins; D012333:RNA, Messenger